A pneumatic-hydraulic converter is required in cases where air is used as a pressure medium in a railway vehicle which employs a hydraulic caliper brake device which uses hydraulic oil as a pressure medium. Accordingly, in recent years, there has developed a tendency to use pneumatic caliper brake devices in order to reduce or eliminate hydraulic power units.
However, in order for railway vehicle to utilize pneumatic caliper brake devices which have lower output than hydraulic caliper brake devices, the pneumatic brake cylinder devices have become larger, which increases the size of the device as a whole, thus making it difficult to install it in a limited space.
Accordingly, the invention of Patent Reference 1 made use of a lever principle in order to enable the use of a small-sized pneumatic brake cylinder.
However, in the pneumatic caliper brake device proposed in Patent Reference 1, a brake head and a brake lining are installed in a floating configuration on the side of one end of a brake lever provided in a railway bogie so that they freely rotate bidirectionally. Therefore, there is a large load on the rotating portions and the sliding portions of the brake lever because of a counter-pressure force and a braking torque which both operate during braking when the brake lever places a load on the brake head and the brake lining Likewise, there is a large load on the brake lever and on the rotating portions and the sliding portions of the brake lever when vibration acts on the caliper brake device, because a pneumatic brake cylinder device provided at the other end of the brake lever is also installed in a floating configuration.
The pneumatic caliper brake device proposed in Patent Reference 1 provides a mechanism adjusting a clearance between the disc and the brake lining within the brake cylinder. Therefore, the operating range of the pneumatic brake cylinder device increases because a protruding length of a pressing rod coupled to the brake lever increases as wear between the disc and the brake lining progresses.